DE Shaw Technology Developer Interview Questions, Process, and Tips

Round duration - 120 Minutes
Round difficulty - Hard

Q1. Number Pattern 3
A high-security meeting has been arranged. Tables for the delegates and security personnel have been arranged. A total of ‘N’ rows of tables has been set up. The first row has one table, t...read more
Ans. Brute Force
The idea here is to traverse all the rows and, for each row, print the suitable character at any particular table.
The steps are as follows:
• We define a ‘RESULT’ matrix.
• We traverse from ‘i’ = 1 to ‘N’, indicating the row number
  • We then traverse from ‘j’ = 1 to ‘i’, indicating the tables of each line.
    • If it is the first or the last character, that is ‘j’ == 1 or ‘j’ == ‘i’, we insert ‘1’ in the ‘RESULT’ matrix.
    • El...read more
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Q2. Minimum Sum in matrix
You are given a 2D matrix ‘ARR’ of size ‘N x 3’ having integers, where ‘N’ is the number of rows.
Your task is to find the smallest sum possible while taking one element from each r...read more
Ans. Brute Force - Recursion
Approach:
• The idea here is to find all possible combinations with the help of recursion.
• Let say we are currently at (i, j). Now we want to move to the (i+1)th row. We can go to any column that means we have a total of 3 options available in that row.
• By the definition of the problem, no two chosen elements belong to the same column. In other words, if we are at (i, j) we can go to (i+1, k) provided...read more
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Q3. Buy and Sell Stock
You are Harshad Mehta’s friend. He told you the price of a particular stock for the next ‘N’ days. You can either buy or sell a stock. Also, you can only complete at most 2-transactions....read more
Ans. Recursion
This problem can be solved by solving its subproblems and then combining the solutions of the solved subproblems to solve the original problem. We will do this using recursion.
Basically, we have to buy the stock at the minimum possible price and sell at the maximum possible price, keeping in mind that we have to sell the stock before buying it again.
 
 
Below is the detailed algorithm: 
 
1. Call ...read more
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Round duration - 90 Minutes
Round difficulty - Medium

Q1. PRETTY JSON
You are given a string 'STR' representing JSON object. Return an array of strings denoting JSON objects with proper indentation.
Rules for proper indentation:
1. Every inner brace sho...read more
Ans. Iterative Approach
The key idea in solving this problem is to simply iterate through the given string and construct our array of strings. We need to take care of the following points:
 
1. Whenever we encounter some kind of opening brace, we add 4 spaces to all the below lines in the beginning
2. Whenever we encounter some kind of closing brace, we delete 4 spaces to all the below lines from the beginning
3. When we encounter a...read more
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Q2. Find Peak Element
Given an array of ‘n’ integers arr. Find the Peak element of the array. The peak element of an array is defined as that element which is greater than both of its neighbours. I.e if arr[i]...read more
Ans. 
1. I gave a O(n) solution doing a basic iteration and comparing each element with its neighbors.
2. But interviewer asked me to optimize further but I was not able to understand how to apply binary search on this
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